二维高聚物振动谱的研究

聚乙炔和聚苯胺通常由于链间耦合比较弱 ,具有一维特性 .但在增加压力的条件下可以使其链间距b减少 ,当达到与晶格常数a相近的程度时 ,这时应考虑其晶格链间耦合作用 ,它们就具有二维复式晶格结构 ,由此会带来新的物理效应 .本文考虑了由于增压作用可以使高聚物晶格链间耦合作用增强 ,并使链间距b减少 ,当b达到与晶格常数a相比拟时 ,它们可以被看作具有二维晶格结构 .基于这种情况建立了理想的二维复式晶格链模型 ,利用晶格动力学的方法 ,计算其晶格链间及原子次近邻间的相互作用 ,借助计算机计算分别在几种晶格链耦合作用下和不同质量比时的色散关系 ,模拟色散曲线 ,讨论第一布里渊区BrillouinZone(BZ)中格波高对称线上频谱的变化 ,分析了由此会带来的新的物理效应 .

A STUDY OF THE VIBRATIONAL SPECTRA OF TWO-DIMENSIONAL POLYMERS

Polyacetylene and polyaniline usually have one-dimensional character because their interchain coupling interaction is weak.As the pressure increases,the interaction also increases and interchain energy gap reduces so that interchain distance b decreases and interchain elastic distance increases.When b approaches the lattice constant a,the polymer of one-dimensional chains becomes a two-dimensional compound lattice structure after considering their interchain coupling action,and new physical properties may arise. In this paper,the second-nearest-neighbor interactions between lattice chains of polyacetylene and polyaniline are considered,and the two-dimensional compound lattice model is adopted.Using the method of lattice dynamics,the dispersion curves of these polymers under different mass ratio are calculated and three kinds of lattice chain interactions are also investigated.The changes of spectra in high symmetric curves under BZ are discussed.We also plot the curve under the various mass ratios.The results show that the two-dimensional compound lattice polymer has two acoustic branches and two optical branches,and the increase of interchain coupling interaction can destroy the effects of aberration of dimerization,and cause the dimensional effect.If interchain coupling interaction is weak and vibration of interchain direction can be neglected,the polymer becomes one-dimensional chain and has only an optical branch and an acoustic branch.